Preparation and Characterization of Vitamin D3-Based Binary Amorphous Systems

Vitamin D3 (VD3) is an essential nutrient for human health that plays a key role in bone health and immune regulation. However, VD3 deficiency has become a common issue worldwide due to insufficient daily intake and inadequate conversion from sunlight exposure. The relatively poor aqueous solubility of VD3 is one of the major challenges in the development of oral supplements and functional foods, since it usually results in low oral absorption. In this study, a total of 11 potential binary systems were prepared by solvent evaporation. The binary amorphous system of VD3 and L-arginine (ARG) has been found to be the most promising binary system, since the VD3-ARG system can significantly improve the solubility of VD3, with an 80-fold enhancement relative to neat crystalline VD3. The amorphization of the VD3-ARG binary system was confirmed and the morphology was observed. Molecular interactions between VD3 and ARG were mainly attributed to hydrogen bonding, and three specific bonding sites were revealed. Furthermore, superior dissolution behavior was observed in the VD3-ARG binary amorphous system compared to the neat VD3. A significantly higher saturation level was achieved and the saturation maintained for the desired period. Overall, this study developed a promising formulation strategy to enhance the solubility of VD3, which can be further applied in functional foods for VD3 supplements.